The present invention relates to a computer system that is equipped with a storage system. More specifically, the present invention relates to a method and device for managing storage system failures in storage area networks (Storage Area Network, hereinafter referred to as a SAN) in which real volumes from a storage system are provided by a server as virtual volumes.
(1) SANs
In recent years, the use of SANs has become more widespread. A SAN is a network dedicated to data storage in which the storage is consolidated and separated from servers in the system. The deployment of SANs makes it possible to provide high-speed data transfer, high scalability and availability in a storage system, as well as efficient usage of storage resources.
(2) SAN Management
The high scalability of SAN-based storage systems allows devices (servers, switches, storage devices) from multiple vendors to be mixed in a SAN. Using a SAN without disruption requires SAN management.
An overview of SAN management is described in p. 331–334 of “Storage Area Network Essentials”, by Richard Barker and Paul Massiglia (John Wiley & Sons, Inc.). In SAN management, the monitoring of the availability of devices connected in the SAN is especially important and is the basis of day-to-day operation of the system. The software used for monitoring SAN availability is hereinafter referred to as the SAN manager. A SAN manager has two major functions: configuration management and failure monitoring.
In the configuration management function, information is periodically obtained from a management agent present in each device that is connected in the SAN, the physical connections (topology) of the SAN are determined from the obtained information, and an up-to-date topology is continuously visualized and provided to the user of the SAN manager, i.e., the SAN administrator.
In failure monitoring, event notifications issued from devices connected in the SAN, e.g., notifications of hardware failure or performance decreases, and device information periodically obtained from the management agent present in each device are used to detect events, such as failures and performance drops, and these events are communicated to the SAN administrator.
With these two functions, the SAN administrator is able to use the SAN manager to provide unified management over availability, thus allowing a reduction in operating costs, e.g., by reducing the number of SAN administrators.
(3) Virtualization Devices
Virtual volumes technology is a SAN storage management technology. Virtual volume technology is disclosed in U.K. laid-open patent application number 2351375, which discloses a device referred to as a storage server that has the following two functions.
1) A function of managing a volume (hereinafter referred to as a real volume), which is a storage region in a storage medium in a storage device connected to the storage server, and for generating a volume pool.
2) A function of generating a virtual volume from at least one real volume in a volume pool, sequentially converting virtual volume I/O requests from the server to real volume I/O requests, and responding to the I/O requests from the server.
The device having these two functions will be referred to hereinafter as a storage virtualization device. By using a virtualization device in a SAN, volume allocations to the server can be centralized using virtual volumes, thus eliminating the need to be aware of the physical arrangement of the storage devices connected to the virtualization device. In other words, the SAN administrator can allocate volumes in a centralized manner.